Motor protector switch



1956 E. ENDERLI 2,766,352

MOTOR PROTECTOR SWITCH Filed Nov. 9, 1953.

Fig.1 L9- United States PatentO MOTOR PROTECTOR SWITCH Ernst Enderli,Emmenbrncke, Lucerne, Switzerland, as-

signor to Weber A.-G., Emmenbrucke, Lucerne, Switzerland ApplicationNovember 9, 1953, Serial No. 391,010

Claims. (CL 200-116) The invention relates to motor protector switchesof the cam operated type, and has the primary object of providing aswitch for the protection of electric motors, particularly for machinetools, against overloads and short circuits.

With this and other objects in view I provide a motor protector switchcomprising in combination: for each pole of the switch an insulatingcarrier body, fixed contacts and movable contact and thermostaticbi-metal elements mounted on each of the said carrier bodies, connectingmeans holding the said carrier bodies together end-to-end in a singlepacket, a control shaft and a release shaft both journalled on the saidpacket of carrier bodies and extending the full thickness thereof, thesaid control shaft operatively controlling the position of the saidmovable contacts relative to the said fixed contacts, and the saidrelease shaft having levers opposite of and controlled by the saidbi-metal elements, a spring biased free release mechanism linked to thesaid control shaft and tending to turn the same into a positionseparating the said movable contacts from the said fixed contacts, and aspring biased pawl normally locking the said free release mechanism inits inoperative position and controlled by the said release shaft, thesaid pawl releasing the said mech-' anism when the said release shaft isturned by the said bi-metal elements bearing on the said levers.

These and other objects and features of the present invention will beclearly understood from the following description of a preferredembodiment of the invention and of a modification thereof given by wayof example with reference to the accompanying drawings, in which:

Fig. 1 is an end elevation of the new motor protector switch, partlybroken off so as to show a detail behind the front plate thereof, i

Fig.2 is a plan view of the said motor protector switch,

Fig. 3 is a section along the line 3--3 of Fig. 2,

Figs. 4, 5 and 6 are sections along the line 44 of Fig. 2 in variousoperational positions, and

Fig. 7 is a section corresponding to Fig. 3 of a modification of theembodiment according to Figs. 1 to 6.

Referring firstly to Figs. 1 to 6, the insulating carrier bodies I carrythe fixed contacts 2 with their terminals 8, the movable contacts 3 withtheir holders 14 and pivots 15, the contact biasing springs 16, thefixing screws 17, as well as the thermostatic bi-metal elements 4 andtheir holders 18. The holders 14 of the movable contacts 3 are connectedto the said bi-metal elements 4 by connecting pieces 19. The releaseshaft 5 passes through the insulating carrier bodies 1 and carrieslevers 20 with adjustment screws 21 cooperating with the respectivebimetal elements 4. The switchor contact-shaft proper 7 carries camdiscs 22 by means of which the movable contacts 3 are operated incooperation with the rollers 23 thereof. Each of these cam discs 22 hasa recess 34 on its circumference.

The front plate 9 forms a shield, indicating the positions 0 and 1 ofthe switch handle which is mounted on the axle 24. A free releasemechanism comprising the linkage 25, 26, 27 and 28 and the release pawl29 with biasing spring 30, and denoted as a whole 11 in Fig. 2, isarranged between the said switch shaft 7 controlling the contacts 3 andthe said switch handle 10. The levers 31 and 32 are fixedly connected tothe shafts 7 and 24, respectively. A biasing spring 33 is attached to apin connecting the front plate 9 to the foremost insulating carrier body1 at one end, and to the joint between the lever 31 and link 25 on theother end.

A cam 36 connected to the said release pawl 29 and to a dial 12 for theadjustment of the critical current intensity is pivoted at the front ofthe foremost insulating carrier body 1 and becomes visible andaccessible upon removal of the switch lever 10 and front plate 9. Thecam 36 cooperates with a leaf spring 37 attached to the release shaft 5.The individual'insulating carrier bodies 1 are held together in a packetby means of screws 13.

In the position illustrated in Fig. 3, the roller 23 of the movablecontact 3 is in juxtaposition to the recess 34 in the cam disc 22 sothat the biasing spring 16 can press the movable contact 3 resilientagainst the fixed contact 2 whereby the current is closed. Thecorresponding position of the switch lever 10 is indicated in Fig. 1,and that of the linkage 25-28, pawl 29 and lever 31 in Fig. 5.

When the switch lever 10 is turned from the position marked 1 on thefront plate 9 into the position marked 0, the said linkage is moved intothe position shown in Fig. 4, and the shaft 7 with the cam discs 22(Fig. 3) is turned in the anti-clockwise direction, whereby the rollers23 are raised out of the recesses 34 and their associated cam discs 22and the movable contacts 3 are lifted off the fixed contacts 2. Theswitch is then in the open position, and the linkage in the position ofFig. 4.

When in the closed position of the switch the current intensity exceedsa predetermined limit (as adjusted by the dial 12) the bi-metal elementsbend downwards, bear on the adjustment screws 21 of the levers 20 andturn the same and the release shaft 5 to which they are attached in theanti-clockwise direction, whereby the leaf spring 37 attached to thesaid shaft 5 turns the cam 36 from the position illustrated in Fig. 5into the position of Fig. 6 against the action of the biasing spring 30whereby the pawl 29 releases the lever 28. The toggle levers 26, 27 andlink 25 accordingly allow the lever 31 to be turned anticlockwise by theaction of the spring 33 whereby the switch shaft 7 is turnedanticlockwise and the contacts 3 are lifted off the contact 2. Thus thecircuit is opened, although the switch lever 10 is in the closedposition. The current intensity at which this free release occursdepends on the initial position of the cam 36 which, as mentioned, canbe adjusted by means of the dial 12.

After a free release, the switch lever 10 has to be turned first fromthe position 1 into the position 0 whereby the linkage is returned intothe position shown in Fig. 4. When the bimetal elements 4 have cooleddown and have retracted into the position shown in Fig. 3, the switchhandle 10 can again be turned to the position 1 whereby the linkagereturns into the position of Fig. 5 and the cam discs 22 and contacts 3return into the position of Fig. 3, so that the switch is closed again.

There are as many insulating carrier bodies 1 as there are poles to becontrolled, for example three of them as shown in Fig. 2 for a threephase alternating current system.

Referring now to Fig. 7, instead of a release shaft 5 passing throughthe insulating carrier bodies 1 as in the embodiment of Figs. 1 to 6, arelease shaft 35 may be provided which passes outside the saidinsulating carrier bodies. Apart from this modification, the arrangementaccording to Fig. 7 corresponds substantially to that of Figs. 1 to 6.

While I have described and illustrated what may be considered typicaland particularly useful embodiments of my said invention, I wish it tobe understood that I do not limit myself to the particular details anddimensions described and illustrated, for obvious modifications willoccur to a person skilled in the art.

What I claim as my invention and desire to secure by Letters Patent, is:

1. A motor protector switch comprising in combination: for each pole ofthe switch an insulating carrier body, fixed contacts and moveablecontacts and thermostatic bi-metal elements mounted on each of the saidcarrier bodies, connecting means holding the said carrier bodiestogether end-to-end in a single packet, a control shaft and a releaseshaft journalled on the said packet of carrier bodies and extending boththe full thickness thereof, the said control shaft operativelycontrolling the position of the said moveable contacts relative to thesaid fixed contacts, and the said release shaft having levers oppositeof and controlled by the said bi-metal elements, a spring biased freerelease mechanism linked to the said control shaft and tending to turnthe same into a position separating the said moveable contacts from thesaid fixed contacts, and a spring biased pawl normally biased forlocking the said free release mechanism in its inoperative position andcontrolled by the said release shaft, the said release shaft beingoperable to move the said pawl against its bias for releasing the saidmechanism when the said release shaft is turned by the said bi-metalelements bearing on the said levers.

2. A motor protector switch as claimed in claim 1, wherein the saidrelease shaft passes through the said packet of insulating carrierbodies.

3. A motor protector switch comprising, in combination, for each pole ofthe switch an insulating carrier body, fixed contacts and movablecontacts and thermostatic bi-metal elements mounted on each of the saidcarrier bodies, connecting means holding the said carrier bodiestogether end-to-end in a single packet, a control shaft and a releaseshaft journalled on the said packet of carrier bodies and extending boththe full thickness thereof, the said control shaft operativelycontrolling the position of the said movable contacts relative to thesaid fixed contacts, and the said release shaft passing outside the saidpacket of insulating carrier bodies and having levers opposite of andcontrolled by the said bi-metal elements, a spring biased free releasemechanism linked to the said control shaft and tending to turn the sameinto a position separating the said movable contacts from the said fixedcontacts, and a spring biased pawl normally locking the said freerelease mechanism in its inoperative position and controlled by the saidrelease shaft, the said pawl releasing the said mechanism when the saidrelease shaft is turned by the said bi-metal elements bearing on thesaid levers.

4. A motor protector switch comprising, in combination, for each pole ofthe switch an insulating carrier body, fixed contacts and movablecontacts and thermostatic bi-metal elements mounted on each of the saidcarrier bodies, connecting means holding the said carrier bodiestogether end-to-end in a single packet, a control shaft and a releaseshaft journalled on the said packet of carrier bodies and extending boththe full thickness thereof, the said control shaft operativelycontrolling the position of the said movable contacts relative the saidfixed contacts, and the said release shaft having levers opposite of andcontrolled by the said bi-metal elements, a spring biased free releasemechanism linked to the said control shaft and tending to turn the sameinto a position separating the said movable contacts from the said fixedcontacts, a spring biased pawl normally locking the said free releasemechanism in its inoperative position and controlled by the said releaseshaft, the said pawl releasing the said mechanism when the said releaseshaft is turned by the said bi-metal elements bearing on the saidlevers, a front plate fixed removably to the said packet of insulatingcarrier bodies spaced from the foremost of the said bodies, a switchhandle pivoted on the said front plate and linked to the said controlshaft, the said front plate carrying marks indicating the position ofthe said switch handle, and the said free release mechanism beingarranged in the space between the said front plate and the foremost ofthe said bodies.

5. A motor protector switch as claimed in claim 4, comprising inaddition: a cam and a dial fixedly connected therewith, both rotatablymounted in the said space and accessible to view and adjustment afterremoval of the said switch lever and front plate, the said cam beingfixedly connected to the said pawl, and a leaf spring mounted on thesaid release shaft resiliently bearing on the said cam in the sense ofturning the said pawl into its release position.

References Cited in the file of this patent UNITED STATES PATENTS2,302,551 Jackson Nov. 17, 1942 2,376,793 Link May 22, 1945 2,416,163Dyer et a1. Feb. 18, 1947 2,418,359 Link Apr. 1, 1947 2,610,272 PlatzSept. 9, 1952 2,669,627 Gelheizer Feb. 16, 1954

